A dome camera including a dome cover is conventionally used as a camera for monitoring in a facility or a building. Such a dome camera is protected from the outside by being covered with a dome cover.
With the need for lower cost, simplified lenses (e.g., a varifocal lens) with a function of adjusting a lens focal point by manual operation have recently been used as lenses for dome cameras. The work of adjusting a lens focal point of a varifocal lens is performed by a user (operator) manually operating a lever for focal point adjustment with a dome cover removed at the time of the work of installing a dome camera. When the work of adjusting the lens focal point of the varifocal lens ends, the user puts the dome cover over the camera.
However, even if a lens focal point of a lens has been appropriately adjusted by lens focal point adjustment work in a conventional dome camera, when the lens is covered with a dome cover, a lens focal point shift occurs due to the lens effect of the dome cover itself (see FIG. 11) to cause blurring in camera footage. A user thus needs to rely on his/her own experience to perform lens focal point adjustment work while taking into account a lens focal point shift. The lens focal point adjustment work involves a process of try and error, such as adjusting a lens focal point and, if blurring is found when the lens is covered with the dome lens, finely adjusting the focal point again.
For this reason, there has conventionally been proposed an imaging apparatus including a lens correction table for correcting for a lens focal point shift as described above (e.g., Patent Literature 1). In the conventional imaging apparatus, a user performs a button operation with a dome cover removed, thereby driving a motor for focal point adjustment to adjust a lens focal point. When the dome cover is put after the lens focal point adjustment, the lens focal point is finely adjusted with reference to the lens correction table. The fine adjustment is performed by driving of the motor for focal point adjustment. A conventional imaging apparatus as described above requires (expensive) components such as memory for storing a table, a motor for focal point adjustment, and a unit for controlling the components and runs counter to the need for lower cost. In addition, not only the focal distance and magnification of a lens but also the type of the lens and the distance to an object need to be taken into account as parameters of a lens correction table in order to appropriately correct for a lens focal point shift using the table. If the lens correction table contains such various parameters, the amount of data in the lens correction table becomes enormous. This results in the need for mass memory (expensive memory) as memory for storing the lens correction table and the difficulty in achieving lower cost.